The present invention relates generally to the packaging art and deals more particularly with an improved self-sealing filler sleeve for a flexible bag suitable for storing fine powdery materials and small size particle and granular products therein, and is of the type provided with a self closing sleeve valve to allow filling the bag with product. Heavy weight paper bags are frequently employed for containing, storing and shipping flowable, fine powdery materials and small sized granular products, such as starch, food products, chemicals, cement and the like. By virtue of the flowable character of these products, such bags are filled by inserting a filler spout of a dispensing machine into an opening of the bag, and the product is delivered from a source thereof through the spout into the bag. Many types of products packaged in this manner may contain dust, or are themselves "dusty" and the dust is easily suspended in the air during movement of the product, as during filling of the bag.
Because the dust from the products is easily suspended within the air, filling operations are sometimes messy, and can even present a health hazard to personnel due to the ambient air being polluted by the product. In addition, when the filled bags are being transported, the vibrations of the carrier, which may be a truck, train or the like, cause the fine powdery material to sift out through the filler opening part of the bag. Consequently, attemps to prevent sifting of the bags' contents through the valve have been made and special valves have been devised in the past to tightly fasten the filler openings of the bag to the dispensing spout during filling operations and to substantially prevent the escape of product from the bag once the dispensing spout is removed from the filler opening. In order to increase production efficiency, these prior art filler valves have been adapted to automatically seal the filler opening after the filling process has been completed.
Prior art bags of the type mentioned above comprise a tubular paper bag closed at both ends, at least one end having a plurality of flaps folded over to define a passageway in the end of the bag which presents an opening at one corner thereof. The flaps are hingedly interconnected to permit the bag to be folded into a flat condition wherein the walls defining the passageway collapse into a face-to-face abutting relationship. A flexible, tubularly shaped sleeve, formed of kraft paper and having a one mil, low density polyethylene film sleeve attached to the inside thereof and extending beyond said kraft paper sleeve is secured within the passageway and extends beyond the latter into the interior of the bag. The entire length of the sleeve is secured to, and between, overlapping flaps which form the closed end of the bag. The dispenser spout is inserted into the sleeve forming the valve and product is dispensed into the bag. After the bag is filled, it may or may not be inverted and the weight of the product in the bag presses against and squeezes the sleeve between opposing flaps thereby closing the sleeve and, thus, the valve.
The primary problem associated with the prior art bags of the type described above is related to the fact that the sleeve valve used in such bags was not "sift-proof" with respect to the product; i.e. the fine powdery material and small sized product within the bag had a tendency to sift out around and through the sleeve thereby escaping from the bag. This was due in part to the fact that wrinkles in the sides of the plastic sleeve were created by the filling operation. These wrinkles formed channels on both sides of the walls of the sleeve through which the product could escape.
Accordingly, it is an object of the present invention to provide an improved filler sleeve for flexible bags which permits filling of the bag with product but which are automatically closable to eliminate the problem of sifting of the product through the sleeve after the bag is filled.
Another object of the present invention is to provide an improved filler sleeve having a sleeve through which the bag may be filled with product and yet which sleeve completely closes after the filling operation in order to positively close the filler passageway through the sleeve and prevent sifting of the product through the sleeve after the bag is filled.